The aim of this study is to examine a method to evaluate the center of foot pressure (CFP) during a static upright posture using the following 4 body-sway factors: unit time sway, front-back sway, left-right sway and high frequency band power. Four body-sway factors were interpreted in a previous study by applying factor analysis to a correlation matrix consisting of 32 parameters representing 6 domains of distance, distribution of amplitude, area, velocity, power spectrum, and body sway vector. Data was gathered from 220 healthy young males and females. The CFP measurement for 1 min was carried out twice with 1 min rest. The measurement device was an Anima's stabilometer G5500. The data sampling frequency was 20 Hz.
It was confirmed that 4 body-sway factors follow a normal distribution and their reliability is very high (ICC=0.89-0.95). After the distribution of each body-sway factor was divided into 4 domains (0-25% (A), 25-50% (B1), 50-75% (B2), and 75-100% (C)), each domain was subdivided into 4 categories. Boundary domains were made up between A and B (1), B (1) and B (2), and B (2) and C (AB, BB and BC). In analyzing trial-to-trial change for each factor, it was confirmed that 74% of the subjects (F3)-97% (Fl) belonged to the same domain. As a result of expanding the range of AB, BB and BC domains to determine each individual's pattern, 95% or more of the subjects could be placed by their positions on 2 trials. Based on the above-stated domain decision method, as a result of examining the change of body-sway for 20 subjects before and after alcohol intake, 65-75% of the subjects showed a domain change in each factor, and all had a body-sway pattern change.
From the above, the convenient evaluation method of body-sway developed in this study was considered to have high reliability and validity, and can synthetically and simply evaluate individual body-sway.
